返回語句C上的SegFault

Question

我在這段代碼中遇到的問題是，當我嘗試在第一次迭代中返回addTrash函數中的struct node * head時。 我懷疑這可能是堆棧損壞，但我不確定，我也不知道我如何確定我給您的代碼中的錯誤。

這是一個雙向鏈接的鏈表，其值僅作為其持有的數據。

struct node * modifyMainList( struct node *head, int link2Delete){

    struct node * curr = head;
    struct node * temp;
    int i = 0;  

    //traverse list link2Delete amount of times
    while(i != link2Delete){

        curr = curr -> next;
    }


    //head case
    if(curr -> previous == NULL){

        curr = curr -> next;            

        head = curr;
        return head;
    }

    //tail case 
    if(curr -> next == NULL){

        temp = curr;    
        curr = curr -> previous;

        curr -> next = NULL;
        temp -> previous = NULL;
        temp -> next = NULL;

        free(temp);
        return head;
    }

    curr -> previous -> next = curr -> next;
    curr -> next -> previous = curr -> previous;            


    curr -> previous = NULL;
    curr -> next = NULL;
    free(curr);
    return head;
}



struct node * addTrash(struct node *mainHead, int link2Delete){

    struct node * head = NULL;
    struct node * curr = mainHead;
    struct node * trashCurr = NULL;;
    struct node * temp = NULL;
    int i = 0;  

    printf("im in trash before loop\n\n");
    for(i = 0; i < link2Delete; i++){

        curr = curr -> next;
    }

    printf("im in trash before head size check\n\n");
    if(head == NULL){

        printf("im in trash with head == null\n\n");
        //head of main list
        if(link2Delete == 0){

            printf("im in trash link2delete == null\n\n");
            curr = curr -> previous;
            head = curr;

            curr = curr -> next;
            curr -> previous = NULL;
            curr -> next = NULL;
            return head;
        }

        printf("im in trash before tail case\n\n");
        //tail of main list
        if(curr -> next == NULL){


            printf("im in trash with tail case\n\n");
            head = curr;

            head -> previous = NULL;
            return head;
        }

        printf("im in trash before after tail case\n\n");

        //every other case

        //printf("this is the head value: %d\n\n", head -> value);
        head = curr;
        //printf("im in trash after head = curr\n\n");

        head -> previous = NULL;
        //printf("im in trash after head -> previous\n\n");

        head -> next = NULL;
        printf("im in trash after head -> next\n\n");

        printf("this is the head value: %d\n\n", head -> value);
        return head;

    }else{

        printf("im in trash inside else\n\n");
        trashCurr = head;
        while(trashCurr -> next != NULL){

            trashCurr = trashCurr -> next;
        }

        if(link2Delete == 0){

            temp = curr; 
            trashCurr -> next = temp;

            temp -> previous = trashCurr;
            trashCurr = temp;
            trashCurr -> next = NULL;
            return head;
        }

        //tail of main list
        if(curr -> next == NULL){

            temp = curr;
            trashCurr = temp;

            temp -> previous = trashCurr;           
            temp -> next = NULL;
            trashCurr -> next = temp;

            return head;
        }

        //every other case

        temp = curr;    
        temp -> previous = trashCurr;

        trashCurr -> next = temp;
        trashCurr = temp;
        trashCurr -> next = NULL;
        return head;

    }


}


void generateRandom(struct node *mainHead, int size){
    int i = 0;
    int link2Delete = 0;
    struct node *head = NULL;
    srand ( time(NULL) );
    int number2Delete = rand() % size + 1;


    printf("this is the rand number: %d\n", rand());    

    printf("this is the number of nodes to be deleted: %d\n", number2Delete);

    for (i = 0; i < number2Delete; i++) {
        // Pick a random node (payload) to delete.  
        link2Delete = (rand() % size);
        printf("this is the number of nodes in the list: %d\n", size);
        printf("this is the node to be deleted: %d\n", link2Delete);
        size--;

        if(link2Delete == 0){
            mainHead = modifyMainList(mainHead, link2Delete);
            //printf("this is the call return: %d\n\n",  addTrash(mainHead, link2Delete) -> value);
            head = addTrash (mainHead, link2Delete);

        }else{

            head = addTrash (mainHead, link2Delete);
            mainHead = modifyMainList(mainHead, link2Delete);
        }

    }
    return;
}

Answer 1

在您的代碼中

while(i != link2Delete){

    curr = curr -> next;
}

如果link2Delete!=0則是一個無限循環。

而且，不是在釋放head case 。

由於循環是無限的，因此curr = curr->next將繼續重復，並將指向某些垃圾指針（如果循環條件為true）。 然后，它具有不確定的行為。 您可能會得到SEGFAULT。